Sunshine drenches San Diego, whatever the season. But the sun doesn’t always shine on San Diego’s football players, even defensive MVPs of the local NFL team. They are to generate their own heat and light. They are to burn in every practice, every game, every season. In reality, there are lulls. For the young, they're called growing pains.

The 2012 NFL season saw Chargers end Corey Liuget, the team’s top draft choice in 2011, emerge as a playmaker and team leader. Liuget was a 300-pound dynamo. He crashed into backfields. He knocked around quarterbacks and running backs. He was only 22 years old, younger than some college seniors. Yet Chargers players named Liuget their defense’s Most Valuable Player.

Another season arrived. Expectations soared.

But in the NFL, sustained success doesn’t just happen.

When Liuget faces the Raiders on Sunday at Qualcomm Stadium, he will be coming off strong performances in his last two games, highlighted by his hit on Peyton Manning that led to Thomas Keiser's interception that sealed the upset of Denver.

Liuget isn’t pleased with his overall performance, though. Too many lulls earlier in the season. The 4.5 sacks, compared with seven last season, is only part of it.

“It’s been about a C-plus, B-average. B-average, I’d say,” he said this week. “Similar to last year, but I believe last year was better for me.

“I just feel a year older, I guess you could say,” he said. “But I’m still playing some good football, and I’m going to continue to get better each and every week.”

Playing solitaire, Liuget may have had a terrific 2013. This wasn’t solitaire. NFL offenses watched film of him. They came to fear him.

“Let’s just say he gets double-teamed a lot,” Chargers defensive coordinator John Pagano said this week.

San Diego’s defensive front underwent an overhaul last offseason, with more changes to come in the preseason and season. The team’s front in 2012 boasted good depth, especially at nose tackle, the lone position between young ends Liuget and Kendall Reyes. Three nose tackles worked in a rotation, keeping all hands fresh. Two of the three left in free agency, and one was an above-average starter in Aubrayo Franklin. End Vaughn Martin, a good backup, also departed.

Reinforcements arrived. One, nose tackle Kwame Geathers, was an undrafted rookie. He needed more time to develop. Others didn't arrive until after training camp, in the case of ends Sean Lissemore and Lawrence Guy, who contributed in time.

An end in San Diego's 3-4 defense sees wider rush lanes when the outside linebacker commands special attention from blockers, as Keiser has of late. Ingram, the Chargers' first draftee in 2012 who was expected to impress this year, didn’t play until Game 13 owing to the torn knee ligament he suffered in May. Freeney’s season-ending injury, in Game 4, deprived the Chargers of a versatile rusher. Freeney's renowned spin move made it more difficult for blockers to gang up on the ends. As it was, the Chargers lacked their top edge rusher of 2012, Shaun Phillips. The Broncos had signed him, cheaply. And he leads them in sacks with 10.

Liuget, for his part, figured he’d help the Chargers more than he has. And he says a shoulder injury suffered in the preseason wasn't to blame.

“I believe I’ve been consistent. I just haven’t been making the plays that I made last year,” he said. “Being able to lay out and make a tackle, a shoestring tackle or whatever -- I haven’t had that many opportunities to make those plays. But I just have to go out and create 'em.”

The coaching and scheme are the same as last year.

Pagano is in his second season as defensive coordinator and Don Johnson is Liuget's line coach for the third year in a row. Just as in recent years, the Chargers have their linemen manage one gap, whereas some defenses, such as the Redskins, run two-gap systems.

Liuget praised his teammates, and improved teamwork. But it is Johnson, he said, who “gets all the credit” for his recent hot streak.

“He’s just on me harder than anything. It’s an everyday effort with him to get better,” he said.

Don’t ever have a setback. Be a pro each and every day.

“That’s what he tells me,” Liuget said.

Pagano approves of the message. It's a message that he says Liuget probably appreciates more than he did a year ago.

“The biggest thing about this profession is, it’s the work that you put in, the Monday through Saturday work, that builds you in your game,” Pagano said. “And then you see the progression.”